Bug 1437360 - do not attempt to parse XHRs as XML if content-length=0, to prevent logging "no root element found" errors; r=smaug

do not attempt to parse XHRs as XML if content-length=0, to prevent logging "no root element found" errors

Differential Revision: https://phabricator.services.mozilla.com/D23444

--HG--
extra : moz-landing-system : lando

dom/base/test/chrome/bug884693.sjs

@@ -1,6 +1,7 @@
 function handleRequest(request, response)
 {
-  let [status, statusText, body] = request.queryString.split("&");
+  let [status, statusText, encodedBody] = request.queryString.split("&");
+  let body = decodeURIComponent(encodedBody);
   response.setStatusLine(request.httpVersion, status, statusText);
   response.setHeader("Content-Type", "text/xml", false);
   response.setHeader("Content-Length", "" + body.length, false);

dom/base/test/chrome/test_bug884693.xul

@@ -19,6 +19,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=884693
 
     const SERVER_URL = "http://mochi.test:8888/tests/dom/base/test/chrome/bug884693.sjs";
     const INVALID_XML = "InvalidXML";
+    const XML_WITHOUT_ROOT = "<?xml version='1.0'?>";
 
     let consoleService = Cc["@mozilla.org/consoleservice;1"].
                          getService(Ci.nsIConsoleService)
@@ -63,7 +64,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=884693
       then(() => { return runTest(205, "Reset Content", INVALID_XML, "", []); }).
       then(() => { return runTest(304, "Not modified", "", "", []); }).
       then(() => { return runTest(304, "Not modified", INVALID_XML, "", []); }).
-      then(() => { return runTest(200, "OK", "", "", ["no root element found"]); }).
+      then(() => { return runTest(200, "OK", "", "", []); }).
+      then(() => { return runTest(200, "OK", XML_WITHOUT_ROOT, XML_WITHOUT_ROOT, ["no root element found"]); }).
       then(() => { return runTest(200, "OK", INVALID_XML, INVALID_XML, ["syntax error"]); }).
       then(SimpleTest.finish);
 

dom/xhr/XMLHttpRequestMainThread.cpp

@@ -1888,6 +1888,15 @@ XMLHttpRequestMainThread::OnStartRequest(nsIRequest* request) {
                    !(mRequestMethod.EqualsLiteral("HEAD") ||
                      mRequestMethod.EqualsLiteral("CONNECT"));
 
+  if (parseBody) {
+    // Do not try to parse documents if content-length = 0
+    int64_t contentLength;
+    if (NS_SUCCEEDED(mChannel->GetContentLength(&contentLength)) &&
+        contentLength == 0) {
+      parseBody = false;
+    }
+  }
+
   mIsHtml = false;
   mWarnAboutSyncHtml = false;
   if (parseBody && NS_SUCCEEDED(status)) {